This invention relates to a molding machine that is used in the production of rubber belts mainly used in power transmission.
Rubber belts of this kind are produced by vulcanizing an unvulcanized rubber portion of a molding in a vulcanizer. A belt includes canvas as the structural member, cords as the tensile element, and an initially unvulcanized rubber sheet which is wound around a mold by a molding machine. The entire assembly is placed in a vulcanizer wherein the assembly is pressurized and heated by high pressure steam to effect crosslinking of the rubber. Then the cross-linked molding together with the mold is removed from the vulcanizer. The mold is separated from the molding, and the molding is cut crosswise into rings of a desired width to produce rubber belts, the final product.
In a conventional typical molding machine, as illustrated in FIG. 4, one end of the core of a mold A is inserted onto the rotary drive shaft 21a of the main spindle head 21, and the other end of the mold A is supported by the tailstock 22. Canvas and cords are would in turn over the mold A by turning the rotary drive shaft 21a, and then an unvulcanized rubber sheet that has been reduced to the desired thickness by a calender roller or the like is wound in multiple layers.
As illustrated in FIG. 5, another molding machine is also known, wherein molds A and B are supported by the respective horizontal shafts 26 of a turret 25 which is rotatable in a horizontal plane on a vertical axis, the turret having a pair of oppositely extending horizontal shafts 26. One end of the mold A is inserted in the rotary drive shaft 21a of the main spindle head 21 to carry out the winding of the canvas, cords, etc. while the other mold B is transferred by a handling machine 27 arranged to be movable close to and away from the turret 25, in order to exchange molds.
Of the aforementioned conventional molding machines, the former needs, when exchanging a mold, to move the mold A held in a horizontal position (laterally) between the main spindle head 21 and the tailstock 22 to a perpendicular position (vertically) and lift the mold A by means of a lifting accessory. A mold after molding can be inserted into a vulcanizer to achieve vulcanization, the next process, only after the central axis of the mold is positioned vertically. Hence the direction (position) of the mold A of which the central axis is horizontal during molding needs to be changed so that the central axis lies vertically. As a result, the exchange of molds is very dangerous, and requires much experience and time, and the work efficiency is also poor since the exchange is made by halting the production line.
In the case of the latter, there is no need to halt the production line since assembly of the molding parts can be made on one mold A while exchange of the other mold B is made simultaneously. Moreover, as the latter is provided with the handling machine 27, there is no need to change the direction of a mold to a vertical position when the mold is to be lifted with the lifting accessory. However, since both of the two molds A and B are supported horizontally relative to the turret 25, the space needed for rotation of the turret 25 to change the left-hand and right-hand positions of the molds A and B with each other is fairly large. Furthermore, a space for installing the handling machine 27, and a space for the handling machine 27 to move towards or away from the turret 25 are also needed. Hence the installation space of the whole installation is very large. Because the operating radius of the installation increases with the installation space, the work efficiency is poor.